DateTime Serialization Returning incorrect Minutes SYMFONY 3

So i created an API with Symfony 3 on JSON , it is working , but the DateTime data's are not returned correctly .

i mean , only the hours are returned correctly but the minutes aren't

This is my Entity , Horaire.php

<?php

namespace CBMedBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use JMS\Serializer\Annotation\ExclusionPolicy;
use JMS\Serializer\Annotation\Expose;
use JMS\Serializer\Annotation\Groups;
use JMS\Serializer\Annotation\VirtualProperty;
use JMS\Serializer\Annotation\Type;